Early techniques for inspecting lenses typically relied on human inspectors to visually examine the lenses for defects (hereinafter referred to as lens defects) usually by placing the lenses under magnification or projection onto a screen whereupon the human inspectors then visually search for lens defects. However, the labour intensive and subjective nature of human operated inspections prompted interest in automating the inspection process. Numerous methods have been investigated, foremost of which are those whereby an image of a lens is acquired and the image then being electronically evaluated for lens defects. Commonly, these methods take advantage of the fact that light, under certain circumstances when encountering a lens irregularity, scatters in a manner that can be qualitatively assessed. These methods generally operate by manipulating a light beam before and/or after passing through a lens in order to extract optical information that is subsequently analysed to assess for flaws.
U.S. Pat. No. 5,500,732 to Ebel et at al and U.S. Pat. No. 6,134,342 to Doke et at describe a conventional system and method for lens inspection. The conventional system and method as described by Ebel and Doke transport lenses using a holder, such as a curvette. However, the conventional system and method is only suited for inspecting lenses that are dry and cannot be applied to inspect ophthalmic or contact lenses that are transported in a medium such as saline solution. Most contact lenses in the market are packaged in saline solution. This causes technical challenges for obtaining high definition images of contact lenses in saline solution for inspection thereof.
As demands for detecting defects of smaller dimension increases, it is necessary to use images of higher resolution to detect such defects. U.S. Pat. No. 6,301,005 to Epstein et al describes a conventional system and method for high resolution lens inspection. However, such high resolution lens inspection requires cameras that are costly and subject to availability. It is therefore difficult to obtain high definition images of the lenses without the use of the foregoing cameras.
Additionally, lens characteristics such as lens power and lens thickness are typically determined after the lenses have been examined for defects. Conventionally, inspection stations are along the lens manufacturing lines in which each inspection station independently measures and determines the corresponding lens characteristics. However, the time spent to transfer the lenses from one inspection station to another adversely affects the efficiency of the lens manufacturing process and hence lowers the overall yield of lens production. Moreover, the need for human intervention during the transferring of lenses from one inspection station to another potentially creates opportunities for human-related mistakes to occur.
Accordingly, there exists a need for a system for addressing the foregoing problems of existing lens inspection systems by minimizing the need to physically transfer the lenses between inspection stations thereby improving the overall efficiency for lens manufacturing.